In an extruder of the generic type known from British patent 1,151,964 a glass fibre strand is introduced into the bore at basically any place, the individual fibres being broken into sections of a predetermined length in the mixing zone. These broken sections are then mixed into the melted plastic material. A disadvantage of this development of an extruder or of the method used by it resides in that the individual fibres are not sufficiently wetted, i.e. the bonding of plastic material and fibres is not of sufficiently good quality. This leads to reduced mechanical properties in any object made from it.
It is known from British patent 988,563 to soak such glass fibre strands--also known as glass silk hanks or rovings--in a melt of the thermoplastic material to be processed or prepared. To this effect this publication cites the above-mentioned method known from British patent 1,151,964 for introducing endless glass fibre strands into plastic material melts.
U.S. Pat. No. 4,439,387 teaches to arrange an apparatus, in which one or several glass fibre strands are coated with plastic material, downstream of the discharge orifice of an extruder for preparing, and more particularly for melting plastic material. These glass fibre strands are introduced laterally into a coating channel by way of inlet nozzles. In this coating channel they pass at least one cam, by which is ensured that the endless fibre strands sufficiently contact the thermoplastic material. They then remain as a central reinforcement inside a compound composite structure.